In a telephone survey involving a sample of 8,937 people aged 18 or over living in Texas, New York and California, Ohayon and researchers found:

That 19.5 percent of U.S. adults reported having moderate to excessive sleepiness, which was comparable between men and women…11 percent of participants reported severe sleepiness, which was more prevalent in women (13 percent) than in men (8.6 percent)… [and] nearly 18 percent of participants reported falling asleep or being drowsy in situations that required a high level of concentration, such as during meetings or conversations.

In a previous study, Ohayon reported that the prevalence of excessive daytime sleepiness in five European countries was 15 percent.

The findings raise concerns for public health and safety, Ohayon told MSNBC:

The number of individuals sleepy or drowsy during situations where they should be alert is disturbing. Sleepiness is underestimated in its daily life consequences for the general population, for the shift workers and for the people reducing their amount of sleep for any kind of good reasons.